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Abstract
The electroreductive conversion of saturated carbohydrates in aprotic media and the subsequent quenching with benzyl bromide results in the formation of benzyl ethers at different C-positions. The application of the semiempirical method AM1 for the calculation of the thermodynamic stability of the intermediate anions formed allows a correct prediction of the observed substitution pattern for the saturated monosaccharides methyl α-d-glucoside, methyl α-d-mannoside, methyl α-d-galactoside, and the unsaturated monosaccharide d-glucal. It is shown that the inclusion of solvent effects via the COSMO continuum model is essential, as it reduces the effect of intramolecular hydrogen bonding as the sole stabilization mode in the gas phase. The results for the disaccharide sucrose are somewhat ambiguous, the three observed substitution positions are among the four most stable calculated anions. This particular system appears to be too complex to be represented by a single conformation.